LONDON – Most babies born in rich countries this century will eventually make it to their 100th birthday, new research says.

Danish experts say that since the 20th century, people in developed countries are living about three decades longer than in the past. Surprisingly, the trend shows little sign of slowing down.

In an article published today in the medical journal Lancet, the researchers write that the process of aging may be “modifiable.”

James Vaupel of the Max Planck Institute in Germany and colleagues in Denmark examined studies published globally in 2004-2005 on numerous issues related to aging. They found life expectancy is increasing steadily in most countries, even beyond the limits of what scientists first thought possible. In Japan, for instance, which has the world’s longest life expectancy, more than half of the country’s 80-year-old women are expected to live to 90.

“Improvements in health care are leading to ever slowing rates of aging, challenging the idea that there is a fixed ceiling to human longevity,” said David Gems, an aging expert at University College London. Gems was not connected to the research.

“Laboratory studies of mice, including our own, demonstrate that if you slow aging even just a little, it has a strong protective effect,” he said. “A pill that slowed aging could provide protection against the whole gamut of aging-related diseases.”

While illnesses affecting the elderly like heart disease, cancer and diabetes are rising, advances in medical treatment are also making it possible for them to remain active longer. The obesity epidemic, however, may complicate matters.